Bad mpg

My GMC Sonoma seems to be getting way less mpg than it should be, its supposed to be getting 14-16 city but it seems I’m getting less than ten. I just got my gas tank repaired due to a leak and they did somewhat of a once over in order for it to pass inspection, but i don’t know why its getting about 8 mpg. please help

an additional question to the problem, could it be a faulty fuel gauge, or sensor

What year Sonoma, engine, and transmission do you have? Is it 4WD or 2WD, and what is the rear end ratio?

And how are you measuring the mileage? Have you ever gotten something close to that 14 - 16 mpg? It could have a lot to do with the load, gearing and your driving style.